Minecraft HDTV and split screen

I bought my son and daughter an HDTV to play split screen minecraft on but it doesn't work...ny ideas? I've put I on widescreen, logged into live I dunno what I'm doing wrong it will not work it's ot an hdmi cable but I dunno....it hd ready f that makes a difference.

Minecraft has a split screen multiplayer mode, but it is only available when the Xbox is outputting HD. The OP is halfway there by having an HDTV, but needs to connect it with an HD capable cable, and set the Xbox to an HD resolution.